Page 1
Exp e ri m e n t al s t u dy of imp rove d r h eology a n d lub rici ty of d rilling
fluids e n h a n c e d wi th n a no-p a r ticle s
Be g, OA, S a n c h ez Espinoza, DE, Kadir, A, S h a m s h u d din, M a n d So h ail, A
h t t p://dx.doi.o rg/1 0.10 0 7/s1 3 2 0 4-0 1 8-0 7 4 6-4
Tit l e Exp e rim e n t al s t u dy of imp rove d r h e ology a n d lub rici ty of d rilling fluids e n h a nc e d wi th n a no-p a r ticles
Aut h or s Beg, OA, S a nc h ez Es pinoz a, DE, Kadir, A, S h a m s h u d din, M a n d Soh ail, A
Typ e Article
U RL This ve r sion is available a t : h t t p://usir.s alfor d. ac.uk/id/e p rin t/46 4 3 7/
P u bl i s h e d D a t e 2 0 1 8
U SIR is a digi t al collec tion of t h e r e s e a r c h ou t p u t of t h e U nive r si ty of S alford. Whe r e copyrigh t p e r mi t s, full t ex t m a t e ri al h eld in t h e r e posi to ry is m a d e fre ely availabl e online a n d c a n b e r e a d , dow nloa d e d a n d copied for no n-co m m e rcial p riva t e s t u dy o r r e s e a r c h p u r pos e s . Ple a s e c h e ck t h e m a n u sc rip t for a ny fu r t h e r copyrig h t r e s t ric tions.
For m o r e info r m a tion, including ou r policy a n d s u b mission p roc e d u r e , ple a s econ t ac t t h e Re posi to ry Tea m a t : u si r@s alford. ac.uk .
Page 2
1
APPLIED NANOSCIENCE
ISSN: 2190-5517
IMPACT FACTOR: 3.325
PUBLISHER: SPRINGER
ACCEPTED: MARCH 26TH, 2018
EXPERIMENTAL STUDY OF IMPROVED RHEOLOGY AND LUBRICITY
OF DRILLING FLUIDS ENHANCED WITH NANO-PARTICLES O. Anwar Bég1*, D.E. Sanchez Espinoza2, Ali Kadir1, MD. Shamshuddin*3 and Ayesha Sohail 4
1Mechanical/Aeronautical Engineering, Salford University, Manchester, M54WT, England, UK.
2 Petroleum Engineering, 228 Malecón del Salado, Guayacanes y Jiguas, Guayaquil, Ecuador.
3Department of Mathematics, Vaagdevi College of Engineering, Warangal, Telangana, India.
4Department of Mathematics COMSATS Institute of Information Technology Lahore 54000, Pakistan.
*Corresponding author: [email protected] , [email protected]
ABSTRACT
An experimental study of the rheology and lubricity properties of a drilling fluid is reported, motivated by
applications in highly deviated and extended reach wells. Recent developments in nanofluids have identified that
the judicious injection of nano-particles into working drilling fluids may resolve a number of issues including
borehole instability, lost circulation, torque and drag, pipe sticking problems, bit balling and reduction in drilling
speed. The aim of this article is therefore to evaluate the rheological characteristics and lubricity of different
nanoparticles in water-based mud, with the potential to reduce costs via a decrease in drag and torque during the
construction of highly deviated and ERD wells. Extensive results are presented for percentage in torque variation
and coefficient of friction before and after aging. Rheology is evaluated via apparent viscosity, plastic viscosity
and gel strength variation before and after aging for water-based muds (WBM). Results are included for silica and
titanium nanoparticles at different concentrations. These properties were measured before and after aging the mud
samples at 80 °C during 16 hours at static conditions. The best performance was shown with titanium nanoparticles
at a concentration of 0.60 % (w/w) before aging.
KEY WORDS: Nano-particles; drilling muds; rheology; lubricity; Titanium; Silica; viscosity; gel strength;
torque.
Page 3
2
1. INTRODUCTION
In the oil and gas industry, drilling is a fundamental and expensive operation. The efficient construction of wells
involves many stages including measurement while drilling (MWD), logging while drilling (LWD), directional
drilling (DD), casing design, cementing, drilling fluids, solids control and maintenance. A key element of the
entire drilling process is drilling fluid engineering which requires carefully fabricated drilling fluid (e.g. muds)
which must perform repeatedly many functions at the same time and over long periods (Gray et al. 1980). Drilling
fluids (muds) serve to cool and lubricate the drilling bit and other critical features include maintenance of an
adequate fluid density, the ability to clean the borehole from drilled cuttings, reducing formation damage (wherein
the drilling mud does not achieve sufficient hydrostatic pressure to mitigate formation fluids from entering into
the well bore), fluid loss, provision of wellbore stability and creating a mud cake. Although petroleum engineers
have developed new methods for due to new challenges in the discovery of new hydrocarbon reserves, there
remain problems related to the performance of drilling muds. These include pipe sticking, drag and torque
increase, erosion of boreholes, formation consolidation, gel formation and lost circulation. These difficulties,
which could delay a continuous operation during drilling, can also result in a huge loss of income for the services
companies due to production down time, waste of material and possibly also environmental hazards. Many
strategies have been developed in recent years to improve the resilience and in particular lubrication properties of
drilling muds. These generally utilize the addition of additives to the drilling mud which is aimed to modify
properties and generate enhanced performance. (Dingsøyr et al. 2004) investigated the use of viscosifiers, wetting
agents and weighting materials to modify the composition and rheology of drilling fluids. (Dantas et al. 2014)
studied experimentally the influence of chemical additives including high-viscosity carboxymethylcellulose
(HV-CMC), calcite and starch on rheological and filtration properties of inhibited drilling fluids composed by
potassium citrate. They found that fluid loss was minimized for drilling fluids comprising starch and calcite in
high concentrations, or with starch, HV-CMC, and calcite in high concentrations. (Qu et al. 2009) presented
laboratory test results for the influence of inhibitive property of polyoxyalkyleneamine (POAM) additive in water-
based drilling fluids, demonstrating reduced toxicity, an improvement in the inhibition of hydration of Na-MMT
and furthermore a reduction in the swelling or hydration of shale cuttings. (Ahmet et al. 2013) investigated a
variety of chemical commercial lubricants on drilling mud (water-based lignosulfonate) rheology and drilling
lubricity using a lubricity tester to evaluate the best lubricity/cost ratio of lubricant compositions, noting that the
presence of high chloride ion content leads to reduced efficiency in drilling fluid lubricity and rheology. Further
studies addressing the modification in drilling fluid lubricity and flow efficiency have been communicated by
(Olatunde et al.2012; Behnamanhar et al. 2014; Slawomir et al. 2009) and for polymeric gel additives in drilling
fluids (Bu et al. 2013).
In recent years nanotechnology has emerged as a vibrant new development in science and engineering.
This involves the manipulation of material properties at the nanoscale. Nanofluids in particular which are
synthesized by the suspension of nano-particles in conventional working fluids (water, oil, mud, coolant etc), have
yielded considerable improvements in many different applications. Introduced by (Choi, 1995) nanofluids have
been shown to dramatically elevate heat transfer properties (such as thermal conductivity, thermal diffusivity) and
via modification in viscosity to improve lubrication performance and heat dissipation in friction processes. Nano-
particles have been successfully implemented in medical engineering (Beg et al. 2017), aerospace systems
(Kannaiyan et al. 2016), heat exchanger technology (Huminic and Huminic, 2012) and solar energy collectors
Page 4
3
(Kaloudis et al. 2016). With a reduction in fabrication costs and customization of different nano-particles for
specific oil fields, nanofluids have recently stimulated some interest in petroleum and gas engineering.
(Amanullah and Al-Abdullatif, 2011) showed that spherical nano-particles introduced in drilling muds can
decrease differential pipe sticking by forming a thin film around the borehole wall and furthermore may help to
dissolve drilling cuttings which aggregate at the base of horizontal well drilling pipes. (Mostafavi et al. 2011)
conducted extensive filtration and rheology tests performed on calcium carbonate and iron hydroxide nano-
particles in invert (water/oil) emulsion drilling fluids, noting the significant capabilities of nano calcium carbonate
to increase the consistency and sealing capabilities of the filter cakes and iron hydroxide nano-particles in reducing
fluid losses. (Ado and Haneef, 2013) reported on the reduction in drilling problems achieved with clay
nanoparticles in drilling fluids for deep hydrocarbon wells in Oman. (Al-Yasiri and Al-Sallami, 2015) identified
the benefits of nano-particles in overcoming the shortcomings of conventional water and oil-based drilling
fluids (gelation, degradation of weighting materials and breakdown of polymeric additives). (Fazelabdolabadi
et al. 2015) studied the fabrication of nano-based drilling fluids from water/oil-based fluids using
functionalized/unfunctionalized (multi-walled) carbon nanotubes (CNT), showing the influence of volume
fraction of CNTs on thermal conductivity, viscosity/yield point, and filtrate amount in all samples. (Zakaria et
al. 2012) described a new class of nanoparticle loss circulation materials for oil-based drilling fluids noting a
considerable decrease in fluid loss with nano-particles, a thinner filter cake which is beneficial for mitigating
formation damage during drilling and also minimizing differential pressure sticking and increased stability of the
drilling fluid.
In the current work, results based on a number of rheological and lubricity tests for several different
nanoparticles added to water-based mud are described. The objective is to establish whether a decrease in drag
and torque is achievable via nanoparticles added to mud which could reduce operational costs in for example
highly-deviated wells. Percentage in torque variation before aging and coefficient of friction before aging are
documented. Rheological characteristics are computed via apparent viscosity and gel strength variation before
aging. It is concluded that improvement in rheological performance can be achieved and that water-based muds
(WBMs) may be modified effectively with different nanoparticles for deployment in actual drilling operations.
We explore the titanium dioxide and silicon dioxide nano-particles which are used to dope water-based drilling
mud. The benefits of these metallic (titanium) and tetravalent metalloid (silicon)-based nano- particles has been
well established in many excellent studies in recent years. These materials have been shown to offer considerable
advantages in numerous technological applications including biomedical (Yang et al. 2015) and energy systems
(Yang et al 2014). Other important studies on nano-particle (e.g. graphene oxide, carbon nanotubes etc) influence
on solubility, mechanical properties and adhesion include Lvov et al. (2011), Jin et al. (2014) and Tian et al.
(2017). The current study is restricted for brevity to the laboratory analysis of only two nano-particles. However,
the methodology is extendable to all of these other advanced nano-materials (and other metallic oxides e.g. zinc
oxide, copper oxide, silver oxide etc) indeed efforts in this regard are continuing at Salford University.
2. METHODOLOGY
2.1 Apparatus and Materials
Page 5
4
The potential of nanoparticles in improving drilling mud properties, as testified to by many of the works reviewed
in Section 1, have motivated experiments to be conducted in the Salford University Petroleum Engineering
Laboratory using silica and titanium nano-particles. These were aimed to evaluate the performance of a water
based drilling mud with nanoparticles at different concentrations, in a lubricity tester to determine if these
additives could be used as friction reduction agents. Since coefficient of friction is a function of temperature, each
sample was heated up at different temperature intervals to analyse its lubricity and rheology before aging, then,
the samples were aged during 16 hours in an oven at high temperature to simulate borehole conditions to check
for variations in the same parameters. A number of different devices were utilized to quantify properties of the
nanoparticles and the drilling muds doped with these particles. A Hamilton Beach high-speed mixer was used to
provide a homogeneous mixture of fine particles through their mechanical dispersion at a high shear rate of about
11500 RPM (data retrieved from FANN, 2016). It was used to mix the drilling fluid and nanoparticles. An
Ultrasonic Bath - DAWE (Type 6444 Sonicleaner) apparatus which uses ultrasound waves propagated through
water was employed to provide a better dispersion of nanoparticles in the WBM. The cavitation phenomenon is
used to disperse nanoparticles in the drilling mud since it creates bubbles that explode and help to break the
formation of clusters in nanoparticles. This sonicator was used after mixing the nanoparticles in the mixer to
prepare the most homogenous mixture possible, as it has been reported that this apparatus reduces the
agglomeration of nanoparticles (Hwang et al. 2008). An OFITE mud balance device was used to provide a direct
reading of the drilling mud density. It has four scales to measure density that are useful for drilling operations:
ppg, SP GR (specific gravity), 𝑙𝑏 𝑓𝑡3⁄ (pounds per cubic feet), PSI/1000ft (pounds per 1000 feet). The method of
operation consists on pouring the drilling fluid into the container, then the lid of the container is placed and some
fluid should pass through the hole of the lid. After, the mud balance is placed on the base that support its knife
edge and the rider, which acts as a counterweight, is moved across the arm until the bubble of the level vial is in
the middle. When equilibrium is achieved, the reading is taken from the different scales. Additionally, its accuracy
is ±0.1 ppg or ±0.01 SP GR (data retrieved from OFITE, 2014). An OFITE Model 800 Viscometer, as shown in
Figure 1, was used to measure the rheological properties of drilling fluids applying a constant shear rate and shear
stress in the drilling mud. This apparatus provides a direct reading of the viscosity, in centipoise (cp), of the
drilling mud through a lighted dial. In addition, it has a speed accuracy of ±0.1 RPM (data retrieved from OFITE,
2014). Via readings obtained at different speeds, some theological parameters can be calculated such as plastic
viscosity, yield point, apparent viscosity and gel strength. The calculations for the first three of these parameters
are made with the following formulae:
• Plastic Viscosity (PV):
cp,readingRPMreadingRPMPV 300600 (1)
• Yield Point (YP):
2100300 tf/bl,PVreadingRPMYP (2)
• Apparent Viscosity (AV):
Page 6
5
cp,readingRPM
AP2
600 (3)
• Gel Strength:
The calculation of the gel strength is taken directly from the dial reading after stopping the apparatus for 10
seconds and 10 minutes, and then turn it on at the speed of 3 RPM (the knob is located on the posit ion of gel). It
is measured in lb 100 ft2⁄ .
Figure 1: Viscometer – Model 800 OFITE used in nano-particle experiments
An OFITE oven was employed to simulate static or dynamic aging of the drilling mud in borehole conditions at
high temperatures and pressures for long periods. This is useful to simulate the behaviour of drilling fluid at the
bottom of the borehole, where temperature and pressure are higher, after the drill string has been removed from
the well for a long time due to different operations, such as a changing the bit, logging evaluation or placing of a
casing section in the well. The oven allows an analysis of the stability of the mud to be performed for realistic
working conditions during which the degradation of the fluid is more drastic. A rectification in mud properties
may be achieved before running a real operation. The method of operation is simple and it can be programmable.
Furthermore, the process of aging is made through an aging cell that keeps the fluid isolated (data retrieved frm
OFITE, 2014). An OFITE lubricity Tester (Figure 2) is also deployed to simulate the increase in torque and
pressure of a drill string when it is exposed to a high deviation angle during a well construction. During these
operations, the drill string tends to settle down at the lower section of the well path. Hence, a section of the drill
string could be in contact with the casing, a rock section or drill cuttings, which lead to an increment in the
coefficient of friction (CoF) and decreased lubricity, if the lubricating film is broken.
Page 7
6
Figure 2: Lubricity Tester (OFI, Houston, Texas, USA)
The lubricity tester measures the lubricity as a function of the CoF of the drilling mud between two solid steel
surfaces: a test ring shaft that turns at a constant speed and the concave groove of a block that is located in a
torque shaft lever arm. This lever arm can be adjusted to the desired torque to press both surfaces. The torque arm
has a handle that can adjust the torque to a maximum of 600 inch-pounds. Therefore, pressures as high as 100,000
psi can be attained depending of the speed of the ring shaft. The lubricity is measured submerging both, the ring
and the block, in a drilling mud sample for a period at a constant speed and torque (of the torque arm). Taking
into account that the distance between the centre of the block and torque bushing is 1.5 inches (as it can be
observed in figure 3), and the standard test is made at 150 inch-pounds, the resulting force applied is 100 lbf.
Moreover, a correction factor needs to be applied since the surfaces of both elements are not always the same.
Therefore, the CoF is calculated dividing the meter reading and the force generated by the block when pressed
against the test ring using the torque arm.
ringtheagainstblocktheofForce
FactorCorrectionreadingMeterCoF
(4)
Here:
ncalibratiowaterDeionizedinobtainedreadingMeter
waterDeionizedforreadingmeterderedtanSFactorCorrection (5)
Additionally, an SEM was used to analyse the dispersion, morphology and composition of nanoparticles in the
base mud after aging them. Other devices implemented in the experiments included a hotplate stirrer for heating
up the drilling mud samples to the desired temperature, a pH meter for controlling the acidity of the mud samples.
Nanoparticles utilised for this experiment were titanium oxide (𝑇𝑖𝑂2), also known as titanium dioxide or titania,
and silicon dioxide (𝑆𝑖𝑂2), also known as silica. Properties are summarized in the Appendix. Both nano-particles
were provided by US Research Nanomaterials, Inc. These materials occur naturally and have been used for
Page 8
7
numerous different applications. They appear due to the normal process of oxidation of the sources where they
are found. In the case of titania which is crystalline, it is found on minerals such as ilmenite, rutile and anatase.
The main source of silica is the mineral quartz, although, it can be found in sand as well. Silica is much more
abundant than titania. These compounds are categorized as ceramic materials since they are oxides and are
therefore hard and brittle. However, the implementation of these materials in drilling muds has not been
investigated rigorously and this is a major motivation for the present work, in particular with regard to rheology
and lubricity in drilling fluids. The Silicon Dioxide (𝑆𝑖𝑂2) nano-particles have an amorphous structure and are
coated with 3-4 % (w/w) KH550 which make them super hydrophilic. The drilling mud used for this experiment
was a WBM classified as a Low-Solids Non-Dispersed (LSND). This drilling mud was used to compare results
before the addition of nanoparticles. The additives used were bentonite, barite and xanthan gum. Each of these
additives performs different functions in this drilling mud. For instance, bentonite is a material made of clay
compounds which swells in the presence of water, so that it is normally used to provide efficient hole cleaning
and prevent fluid loss into the formation, moreover, is the most common additive used in WBM. Barite is
composed by Barium Sulphate and it is utilised as a weighting agent to increase the density of the drilling mud.
Xanthan gum is a polymer generated by bacteria and it is used to increase the viscosity of drilling fluids when
their density is low.
2.2 Experimental Procedures
The following diagram depicts the four stages to the experiments conducted. Firstly, the drilling mud was prepared
using the additives mentioned and its rheology and lubricity was evaluated before and after aging. Then, four mud
samples were mixed to add two different concentrations of each of the nano-particles and the same tests were
performed on them.
Figure 3: Experimental Procedure
2.2.1 Drilling Fluid Preparation
1. In the cup of the mixer were added 350 ml of distilled water and 15 grams of bentonite. This mixture was
stirred for 15 minutes approximately. It was then left at rest for the same amount of time to allow clay
hydration.
2. Next 15 grams of Barite were added to increase the density of the fluid, and it was mixed for five minutes.
Addition of Nanoparticles
Drilling Fluid
Preparation
• Before Aging
• After Aging
Analysis of Rheology
and Lubricity
Page 9
8
3. Finally, 0.7 grams of xanthan gum were added in small portions to avoid the formation of lumps in the drilling
mud and produce a more homogeneous mixture. This was stirred for 10 minutes and left at rest for the same
amount of time.
Figure 4: Drilling Fluid Preparation
2.2.2 Addition of Nanoparticles
1. After preparing the drilling fluid and left at rest for some time, nanoparticles were added to the drilling mud
in the following concentrations (Table 1) for each mud sample of 350 ml:
2. Then, the nanoparticles were mixed in the drilling fluid using two different two-step methods: stirring and an
ultrasonic agitation.
3. When using the mixer, nanoparticles were stirred at high speed during 40 minutes.
4. Soon after, they were introduced in the ultrasonic bath using Erlenmeyer flasks, as it can be observed in the
following figure:
5. After 30 minutes, the ultrasonic bath was stopped and the samples were left to rest at room temperature.
Figure 5: Addition of nanoparticles in the drilling fluid
Table 1: Nano-particle concentrations
Nanoparticles Concentration (w/w %)
2OTi
0.20
0.60
2OSi
0.20
0.60
350 ml Distilled Water
15 gr Bentonite
15 gr Barite
0.7 gr Xanthan
Gum
Drilling Fluid
Drilling FluidAddition of
NanoparticlesStirrer
(40 minutes)
Ultrasonic Agitation
(30 minutes)
Page 10
9
2.2.3 Analysis of Rheology and Lubricity before Aging
Drilling fluid samples before and after adding nanoparticles were evaluated in the same way.
1. After drilling fluid samples were cooled down to 26 °C, density, rheology and lubricity was measured using
the mud balance, viscometer and lubricity tester, respectively.
2. The rheology was measured observing a stable value in the dial reading at 600, 300, 200, 100, 60, 30 and 6
RPM. Gel strength was measured observing the maximum deflection in the dial reading at 3 RPM when the
viscometer was turned on at this speed after the mud sample was left at rest for 10 seconds and 10 minutes.
3. The lubricity test was carried out calculating the correction factor for the lubricity ring and lubricity block
and observed each minute during 6 minutes.
4. Then, the fluid samples were heated up in the hotplate stirrer at 40, 60 and 80 degrees Celsius (°C), and the
same tests were performed to simulate the mud samples behaviour during drilling operations.
Figure 6: Analysis performed before aging
2.2.4 Analysis of Rheology and Lubricity after Aging
1. The drilling fluid samples (with and without nanoparticles) were poured into aging cells.
2. Then, they were placed in the oven for 16 hours at 80 °C. The samples remained static during this period to
simulate bottom hole conditions.
3. After this time, the samples were cooled down to 26 °C and its rheology was evaluated. Then, the samples
were stirred in the mixer for 10 minutes and its rheology was tested again, as well as its lubricity using the
same procedure for the samples before aging.
In addition, during the drilling fluid preparation, the pH level of the mixture was continuously checked with the
pH meter to maintain it at 10 via the addition of caustic soda.
Drilling Fluid
• No Nanoparticles
• 𝑇𝑖𝑂2
• 𝑆𝑖𝑂2
Temperature (°C)
• 25
• 40
• 60
• 80
Tests
• Density
• Rheology
• Lubricity
Page 11
10
Figure 7: Aging cells and oven
Figure 8: Analysis performed after aging
3. RESULTS
After preparing the mud samples and following the procedure described above, extensive results were derived for
density and rheology characteristics.
3.1 Density Results
Below Table 2 presents the results obtained for the densities of all 5 mud samples in different units, as well as the
temperature and pH of the samples.
Table 2: Densities of mud samples
DENSITY
SAMPLE PPG SP GR lb/ft3 PSI/1000 ft T (°C) PH
BASE MUD 8.83 1.06 66.14 458.98 26 10
TiO2 0.20 % 8.83 1.06 66.14 458.98 26 10
TiO2 0.60 % 8.83 1.06 66.14 458.98 26 10
SiO2 0.20 % 8.85 1.062 66.27 459.85 26 10
SiO2 0.60 % 8.90 1.068 66.64 462.44 26 10
Drilling Fluid
•No Nanoparticles
•𝑇𝑖𝑂2
•𝑆𝑖𝑂2
Before Stirring
•Rheology
After Stirring
•Rheology
•Lubricity
Page 12
11
3.2 Rheology Results
3.2.1 Before Aging
The results of the RPM, viscosity and gel strength rheology obtained for each of the original and 4 nano-particle
doped mud samples (2 each for titania and silica nano-material) is detailed below, prior to aging. A graph of the
shear stress vs the shear rate (RPM) for the different temperatures is also provided to show the trend of the mud
samples.
Base Mud:
Table 3: Gel strength rheology of base mud [cP=centiPoise]
RHEOLOGY
BASE MUD
VISCOSITY (cP)
TEMPERATURE (°C)
TEMP 26 °C 40 °C 60 °C 80 °C
RPM (rad/s)
600 46.5 43 43.5 42
300 33 31 31 30
200 27 26 26 24.5
100 20.5 20 19 17.5
60 17 17 15.5 14.5
30 14 13.5 13 11.5
6 10 10 8.5 7.5
GEL STRENGTH
(𝒍𝒃 𝟏𝟎𝟎 𝒇𝒕𝟐⁄ )
10 sec 9.5 9 7 7
10 min 14 14 12 14.5
Page 13
12
Figure 9: Shear stress rheology of base mud (C = degrees Celsius)
Base Mud with 0.20% (w/w) 2OTi :
Table 0: Gel strength rheology of base mud with 0.20% (w/w) 2OTi [cP=centiPoise]
TiO2 (0.20% w/w)
VISCOSITY (cP)
TEMPERATURE (°C)
26 °C 40 °C 60 °C 80 °C
RPM (rad/s)
600 50 49.5 47.5 51.5
300 35.5 35 34 37
200 29.5 29.5 28.5 31
100 22.5 22.5 21.5 23
60 19 19 18.5 19
30 15.5 15.5 15 16
6 10.5 10.5 10.5 11
GEL STRENGTH
(𝒍𝒃 𝟏𝟎𝟎 𝒇𝒕𝟐⁄ )
10 sec 9.5 9.5 8.5 9.5
10 min 14.5 14.5 14 16.5
0
5
10
15
20
25
30
35
40
45
50
0 100 200 300 400 500 600 700
SHEA
R S
TRES
S, l
b/1
00
ft2
RPM (rad/s
RHEOLOGY - BASE MUD
28.2 C 40 C 60 C 80 C
Page 14
13
Figure 10: Rheology of base mud with 0.20% (w/w) 𝑇𝑖𝑂2(C = degrees Celsius)
Base Mud with 0.60% (w/w) 2OTi :
Table 5: Gel strength rheology of base mud with 0.60% (w/w) 2OTi [cP=centiPoise]
RHEOLOGY
TiO2 (0.60% w/w)
VISCOSITY (cP)
TEMPERATURE (°C)
26 °C 40 °C 60 °C 80 °C
RPM (𝒔−𝟏)
600 53.5 50.5 50.5 53.5
300 38 37 37.5 38.5
200 32.5 31.5 32 33
100 25 24.5 25 25.5
60 21 21 21 22
30 17.5 18 18 18.5
6 12.5 13 13 14
GEL STRENGTH
(𝒍𝒃 𝟏𝟎𝟎 𝒇𝒕𝟐⁄ )
10 sec 12 11 10 11.5
10 min 16 16.5 16.5 19.5
0
10
20
30
40
50
60
0 100 200 300 400 500 600 700
SHEA
R S
TRES
S, l
b/1
00
ft2
RPM (rad/s)
RHEOLOGY - TiO2 0.20%
26 C 40 C 60 C 80 C
Page 15
14
Figure 11: Shear stress rheology of base mud with 0.60% (w/w) 2OTi (C = degrees Celsius)
Base Mud with 0.20% (w/w) 𝑺𝒊𝑶𝟐:
Table 6: Gel strength rheology of base mud with 0.20% (w/w) 2OSi
RHEOLOGY
SiO2 (0.20% w/w)
VISCOSITY (cP)
TEMPERATURE
26 °C 40 °C 60 °C 80 °C
RPM (rad/s)
600 46 41 38.5 39.5
300 31.5 29.5 28 27.5
200 26.5 24.5 22.5 22
100 19.5 18.5 16.5 15.5
60 16 15.5 13 12
30 12.5 12 10.5 9.5
6 8 7.5 5.5 5.5
GEL STRENGTH
(𝒍𝒃 𝟏𝟎𝟎 𝒇𝒕𝟐⁄ )
10 sec 8.5 8 6 6
10 min 11.5 10.5 8.5 8
0
10
20
30
40
50
60
0 100 200 300 400 500 600 700
SHEA
R S
TRES
S, l
b/1
00
ft2
RPM (rad/s)
RHEOLOGY - TiO2 0.60%
26 C 40 C 60 C 80 C
Page 16
15
Figure 12: Rheology of base mud with 0.20% (w/w) 𝑆𝑖𝑂2 (C = degrees Celsius)
Base Mud with 0.60% (w/w) 2OSi :
Table 7: Rheology of base mud with 0.60% (w/w) 2OSi
RHEOLOGY
SiO2 (0.60% w/w)
VISCOSITY (cP)
TEMPERATURE
26 °C 40 °C 60 °C 80 °C
RPM (rad/s)
600 49 43.5 41 41
300 33.5 30.5 28.5 27
200 27 25.5 23.5 27.5
100 19.5 19 17.5 15.5
60 16 15.5 14.5 12
30 13 12.5 10.5 9
6 8.5 8 6 5
GEL STRENGTH
(𝒍𝒃 𝟏𝟎𝟎 𝒇𝒕𝟐⁄ )
10 sec 9 8 7 6
10 min 11 10 9 7.5
0
5
10
15
20
25
30
35
40
45
50
0 100 200 300 400 500 600 700
SHEA
R S
TRES
S, l
b/1
00
ft2
RPM (rad/s)
RHEOLOGY - SiO2 0.20%
26 C 40 C 60 C 80 C
Page 17
16
Figure 13: Rheology of base mud with 0.60% (w/w) 𝑆𝑖𝑂2(C = degrees Celsius)
3.2.2 After Aging
After aging the mud samples for 16 hours at 80 °C, the samples were cooled down to 26 °C. Following this the
rheological experiments were re-conducted again at one temperature before and after stirring.
3.2.2-1 Before Stirring
Table 8: Rheology of aged mud samples before stirring
RHEOLOGY
AFTER AGING - BEFORE STIRRING
VISCOSITY (cP)
MUD SAMPLE
BASE
MUD
TiO2
0.20%
TiO2
0.60%
SiO2
0.20%
SiO2
0.60%
RPM (rad/s)
600 39 50 44 54 63.5
300 26.5 35 30.5 38 44.5
200 21 28 24.5 30.5 35.5
100 14 20 17.5 21 25.5
60 11 16 14 17.5 19.5
30 8.5 12 10.5 12.5 14.5
6 5 7 7 6.5 8
0
10
20
30
40
50
60
0 100 200 300 400 500 600 700
SHEA
R S
TRES
S, l
b/1
00
ft2
RPM (rad/s)
RHEOLOGY - S IO2 0.60%
26 C 40 C 60 C 80 C
Page 18
17
GEL
STRENGTH
(𝒍𝒃 𝟏𝟎𝟎 𝒇𝒕𝟐⁄ )
10 sec 5 6.5 7 6 8
10 min 7 9.5 9 7.5 9
Figure 14: Rheology of aged mud samples before stirring
3.2.2-2 After Stirring
Table 9: Rheology of aged mud samples after stirring
RHEOLOGY
AFTER AGING - AFTER STIRRING
VISCOSITY (cP)
MUD SAMPLE
BASE
MUD
TiO2
0.20%
TiO2
0.60%
SiO2
0.20%
SiO2
0.60%
RPM (rad/s)
600 26.5 34.5 32 33 38.5
300 18 24 22 22 26
200 15 19.5 18 18.5 20.5
100 10.5 13.5 13 12 14.5
60 7.5 11 10 8.5 11
30 5.5 8 7.5 6 8
6 3 4.5 4 3.5 4.5
10 sec 4 4.5 5 4.5 5
0
10
20
30
40
50
60
70
0 100 200 300 400 500 600 700
SHEA
R S
TRES
S, l
b/1
00
ft2
RPM (rad/s)
RHEOLOGY - AGED SAMPLES BEFORE STIRRING
BASE MUD TiO2 0.20% TiO2 0.60%
SiO2 0.20% SiO2 0.60%
Page 19
18
GEL
STRENGTH
(𝒍𝒃 𝟏𝟎𝟎 𝒇𝒕𝟐⁄ )
10 min 7 7 8 6 7
Figure 15: Rheology of aged mud samples after stirring
3.3 Lubricity Results
Before evaluating the mud samples, the correction factor for the lubricity ring and lubricity block was calculated
using equation (5). The result obtained is shown below:
94036
34.FactorCorrection (6)
3.3.1 Before Aging
Similar to the rheology tests, the lubricity of the original and 4 nano-doped mud samples were evaluated at
different temperatures as well. In this case, the data extracted is the torque reading. The following tables and
graphs show the torque readings of the mud samples at different temperatures. The analysis of the lubricity is then
subsequently conducted.
Base Mud:
Table 10: Torque readings of base mud
LUBRICITY TEST
BASE MUD
TEMPERATURE
TIME (min) 26 °C 40 °C 60 °C 80 °C
TORQUE
READING
1 37.5 42.3 45.2 43.6
2 39.5 42.4 44.4 44.4
0
10
20
30
40
50
0 100 200 300 400 500 600 700
SHEA
R S
TRES
S, l
b/1
00
ft2
RPM (rad/s)
RHEOLOGY - AGED SAMPLES AFTER STIRRING
BASE MUD TiO2 0.20% TiO2 0.60%
SiO2 0.20% SiO2 0.60%
Page 20
19
(inch-pounds) 3 40 42 44.4 45.5
4 40 41.4 44.6 45.8
5 39.9 40.7 44.6 46.1
6 39.6 41.1 45 46.6
Figure 16: Torque readings of base mud (C = degrees Celsius)
Base Mud with 0.20% (w/w) 2OTi :
Table 11: Torque readings of base mud with 0.20% (w/w) 2OTi
LUBRICITY TEST
TiO2 (0.20% w/w)
TEMPERATURE
TIME (min) 26 °C 40 °C 60 °C 80 °C
TORQUE
READING (inch-
pounds)
1 42.4 42.7 47.9 44.4
2 44.5 43.3 48.5 44.6
3 44.2 44.1 48.6 44.4
4 44.6 45.2 48.4 46.3
5 45.9 46 47.7 45.7
6 46.1 45.3 47 45.6
35.5
37.5
39.5
41.5
43.5
45.5
47.5
0 1 2 3 4 5 6 7
TOR
QU
E, I
NC
H-P
OU
ND
S
TIME, MIN
BASE MUD
26 40 C 60 C 80 C
Page 21
20
Figure 17: Torque readings of base mud with 0.20% (w/w) 2OTi (C = degrees Celsius)
Base Mud with 0.60% (w/w) 2OTi :
Table 12: Torque readings of base mud with 0.60% (w/w) 2OTi
LUBRICITY TEST
TiO2 (0.60% w/w)
TEMPERATURE
TIME (min) 26 °C 40 °C 60 °C 80 °C
TORQUE
READING (inch-
pounds)
1 40.2 39.2 39.3 39
2 40 37.7 38.4 39.4
3 40 37.4 37.9 39.3
4 39.3 36.7 37.6 39.4
5 38.7 35.9 37.6 39
6 37.9 36.2 37.4 39.6
35.5
37.5
39.5
41.5
43.5
45.5
47.5
49.5
0 1 2 3 4 5 6 7
TOR
QU
E, I
NC
H-P
OU
ND
S
TIME, MIN
T IO2 0.2
26 C 40 C 60 C 80 C
Page 22
21
Figure 18: Torque readings of base mud with 0.60% (w/w) 𝑇𝑖𝑂2(C = degrees Celsius)
Base Mud with 0.20% (w/w) 2OSi
Table 13: Torque readings of base mud with 0.20% (w/w) 2OSi
LUBRICITY TEST
SiO2 (0.20% w/w)
TEMPERATURE
TIME (min) 26 °C 40 °C 60 °C 80 °C
TORQUE
READING (inch-
pounds)
1 37 40.6 42.5 43.9
2 38.8 41.2 42.7 44.5
3 39.1 42.3 43.3 44.1
4 39.8 42.5 43.9 44.7
5 40.7 42.8 43.6 44.7
6 40.2 43.1 43.4 44.2
35.5
36
36.5
37
37.5
38
38.5
39
39.5
40
40.5
0 1 2 3 4 5 6 7
TOR
QU
E, I
NC
H-P
OU
ND
S
TIME, MIN
T IO2 0.60%
26 C 40 C 60 C 80 C
Page 23
22
Figure 19: Torque readings of base mud with 0.20% (w/w) 𝑆𝑖𝑂2 (C = degrees Celsius)
Base Mud with 0.60% (w/w) 2OSi :
Table 14: Torque readings of base mud with 0.60% (w/w) 2OSi
LUBRICITY TEST
SiO2 (0.60% w/w)
TEMPERATURE
TIME (min) 26 °C 40 °C 60 °C 80 °C
TORQUE
READING (inch-
pounds)
1 47 43.2 43.9 44.8
2 46.2 41.6 44.7 44.4
3 45.2 41 44 43.7
4 43.8 40.6 43.7 43.5
5 42.6 40 43.2 43.1
6 43.4 40.4 43.1 42.8
35.5
36.5
37.5
38.5
39.5
40.5
41.5
42.5
43.5
44.5
45.5
0 1 2 3 4 5 6 7
TOR
QU
E, I
NC
H-P
OU
ND
S
TIME, MIN
S IO2 0.20%
26 C 40 C 60 C 80 C
Page 24
23
Figure 20: Torque readings of base mud with 0.60% (w/w) 𝑆𝑖𝑂2(C = degrees Celsius)
3.3.2 After Aging
The lubricity test was repeated for all 5 mud samples after the aging process and stirring them in the mixer for 10
minutes. The results are shown below.
Table 15: Torque readings of aged mud samples after stirring
LUBRICITY TEST
AFTER AGING - AFTER STIRRING
MUD SAMPLES
TIME
(min)
BASE
MUD
TiO2
0.20%
TiO2
0.60%
SiO2
0.20%
SiO2
0.60%
TORQUE
READING
1 28 36.5 33.1 40.4 37.5
2 32.9 35.8 33.6 38.8 38.4
3 34.1 36.8 33.6 37.8 38
4 34.8 36.1 33.8 37.1 38.4
5 34.3 36 33.7 37.3 38.4
6 34.1 35.9 33.9 36.9 38
35.5
37.5
39.5
41.5
43.5
45.5
47.5
49.5
0 1 2 3 4 5 6 7
TOR
QU
E, I
NC
H-P
OU
ND
S
TIME, MIN
S IO2 060%
26 C 40 C 60 C 80 C
Page 25
24
Figure 21: Torque readings of aged mud samples after stirring
4. ANALYSIS AND DISCUSSION
In this section, we interpret the results presented earlier. Each set of results pertaining to different aspects of the
investigation is addressed individually i.e. density, rheology and lubricity. The density unit used is that consistent
with modern petroleum engineering, namely lbm/gal (also known as ppg i.e. pounds per gallon).
4.1 Density
Inspection of table 2 reveals that density of the mud samples was very similar after the addition of nanoparticles.
There was only a small increase when silica nanoparticles were added, while the variation in concentration of
titania nanoparticles did not show any tangible alteration. This increment observed with silica nanoparticles was
proportional to the concentration of these nano-particles in the base mud, and this has been calculated and listed
in Table 16. These results suggest that silica nanoparticles could have acted as weighting agents which could be
applicable in actual water-based mud suspensions in the field where even a slight modification in density may be
beneficial to drilling (Mostafavi et al. 2011).
Table 16: Variation in density with nanoparticles
25
27
29
31
33
35
37
39
41
43
0 1 2 3 4 5 6 7
TOR
QU
E, I
NC
H-P
OU
ND
S
TIME, MIN
TORQUE - AGED MUDS AFTER STIRRING
BASE MUD TiO2 0.20% TiO2 0.60% SiO2 0.20% SiO2 0.60%
SAMPLE PPG INCREASE (%)
BASE MUD 8.83 -
TiO2 0.20 % 8.83 0
TiO2 0.60 % 8.83 0
SiO2 0.20 % 8.85 0.23
SiO2 0.60 % 8.90 0.79
DENSITY
Page 26
25
4.2 Rheology- before aging
In general, the results of the rheology tests (before aging) of the mud samples doped with nano-particles, which
are plotted from figures 10-15 demonstrate the normal trend of typical drilling muds i.e. without nano-particles
(sample 1, figure 9). The analysis of the rheological properties was done using the Bingham (viscoplastic) model
and the curves of each mud sample were adapted to this model. However, this model is not representative of the
drilling mud behaviour at low shear rates. The plastic viscosity, yield point and apparent viscosity were calculated
using equations (1), (2) and (3), respectively. An example of the calculation of these parameters for the base mud
at 26 °C follows:
Plastic Viscosity:
cp..readingRPMreadingRPMPVcBase
51333546300600 026Mud (7)
Yield Point:
210051951333300 tf/lb..PVreadingRPMYP
cBase0
26Mud (8)
Apparent Viscosity:
cp..readingRPM
AVcBase
25232
546
2
6000
26Mud (9)
The same procedure was repeated for the other results obtained in Tables 3-9.
Table 17: Results of PV, YP, YP/PV and AV of mud samples before aging
Page 27
26
Table 17 summarizes these calculations using the Bingham model (a yield stress is required to initiate flow), and
presents the increase (green arrow) and decrease (red arrow) of these parameters compared to the base mud
(yellow dash) for each temperature. The evaluation of the rheology at different temperatures showed that the
viscosity readings were different for each case, although, they were close to the base mud results. From figures
9-13, it is evident that titania nanoparticles provided higher viscosity than base mud or silica-doped mud. Silica
nanoparticles infact reduced the viscosity of the mud. In general, the viscosity of all the mud samples tended to
increase at high shear rates. Moreover, in the case of silica nanoparticles and base mud, the viscosity was reduced
when the temperature was increased. However, in the case of titania nanoparticles, it is apparent that the variations
of viscosity at different shear rates remained almost the same for all the temperatures. A possible explanation for
this behaviour is that silica nanoparticles are hydrophilic, so that the amount of solid particles in the base mud is
infact drastically reduced and they do not improve therefore the viscosity of the base mud as titania nano-particles.
It is also important to note that in general, titania nanoparticles showed an increase in plastic viscosity (PV), yield
point (YP) and apparent viscosity (AV), although they exhibit a decrease in yield point when the concentration is
lower i.e. 0.20% (w/w) at 40 °C. The addition of silica nanoparticles results in a decrease in the yield point, and
a similar trend in apparent viscosity although there is a deviation from this at a concentration of 0.60% (w/w)
where viscosity increases at 26 °C and 40 °C. Some fluctuation in results is also evident with temperature and a
consistent trend is not attained for plastic viscosity with silica. Plastic viscosity tends to increase in drilling fluids
due to an excess in the number of particles, which in turn causes an increase in the mechanical friction between
solids and liquids in the mud system (Baker Huges 1995). Taking into account this antecedent and the
T (°C) SAMPLE PV (CP) YP (lb/100 ft2) YP/PV AV (cp)
BASE MUD 13.5 19.5 1.44 23.25
TiO2 0.20% 14.5 21 1.45 25
TiO2 0.60% 15.5 22.5 1.45 26.75
SiO2 0.20% 14.5 17 1.17 23
SiO2 0.60% 15.5 18 1.16 24.5
BASE MUD 12 19 1.58 21.5
TiO2 0.20% 14.5 10.5 0.43 29.75
TiO2 0.60% 13.5 23.5 1.74 25.25
SiO2 0.20% 11.5 18 1.57 20.5
SiO2 0.60% 13 17.5 1.35 21.75
BASE MUD 12.5 18.5 1.48 21.75
TiO2 0.20% 13.5 20.5 1.52 23.75
TiO2 0.60% 13 24.5 1.88 25.25
SiO2 0.20% 10.5 17.5 1.67 19.25
SiO2 0.60% 12.5 16 1.28 20.5
BASE MUD 12 18 1.50 21
TiO2 0.20% 14.5 22.5 1.55 25.75
TiO2 0.60% 15 23.5 1.57 26.75
SiO2 0.20% 12 15.5 1.29 19.75
SiO2 0.60% 14 13 0.93 20.5
26
40
80
60
RHEOLOGY
PV - YP - AV
BEFORE AGING
Page 28
27
concentrations used for each nanoparticle, 0.20 % (w/w) and 0.60 % (w/w), and assuming that the morphology of
both nanoparticles was spherical the number of titania particles per 350 ml was roughly 1.17× 1016 and
3.51× 1016, respectively. However, the number of silica particles for the same amount of liquid was about
6.33× 1016 and 19.01× 1016 which is significantly larger and may be counter-productive for mud rheology.
Furthermore, the calculation is not exact since the structure of both nanoparticles are not exactly spherical, as
described in the property tables given in the Appendix, but approximations. A visualization of the variation of
plastic viscosity for all five samples is given in Figure. 22
Figure 22: Plastic viscosity before aging
In the case of silica nanoparticles, the super hydrophilic characteristic (due to their coating agent) may have
reduced the amount of solid silica nanoparticles dispersed in the drilling mud. The plastic viscosity achieved when
titania was added almost invariant with different temperatures and did not follow the normal decreasing trend of
the base mud. A normal mud tends to decrease in plastic viscosity when its temperature is raised since the viscosity
of the water decreases (Baker Huges, 1995). This effect may furthermore contribute to improved thermal
conductivity of titania nanoparticles in the base mud. Regarding the yield point, this parameter is an indicator of
the chemical attraction of the particles in the drilling mud. When the balance is broken, the yield point tends to
increase. This may arise due to the addition of inert solids and the volume concentration of solids although many
other micro-structural features may also contribute. In the case of titania nanoparticles, these nano-particles may
not have interacted with the rest of the additives, acting as inert particles, in the drilling mud which may manifest
in an increase in yield point. In the case of silica nanoparticles, the super hydrophilic feature could have caused a
reduction in yield point since these particles were probably dissolved in the drilling mud, which is water-based
which results in a decrease in volume concentration of solids. Therefore, the addition of titania nanoparticles in
the base mud indicates that this nano-particle doped mud sample requires greater shear stress to initiate motion of
the drilling mud, as shown in figure 23. Conversely the addition of silica nanoparticles requires less stress for
mobilizing flow of the drilling mud. Although lower yield stress may have advantages it can also lead to problems
in the reduced ability of the drilling mud to suspend drill cuttings when drilling.
0
2
4
6
8
10
12
14
16
18
26 40 60 80
PV
, cP
TEMPERTATURE, °C
PLASTIC VISCOSITY
BASE MUD
TiO2 0.20%
TiO2 0.60%
SiO2 0.20%
SiO2 0.60%
Page 29
28
Figure 23: Yield point before aging
The relationship between both parameters (YP PV⁄ ), yield point and plastic viscosity, is useful to determine the
efficiency of the drilling mud when cleaning the well. A low plastic viscosity and a high yield point give an
optimum efficiency. The results in figure 24 show that titania nanoparticles achieve the highest increase in this
relationship, which is proportional to the increase in concentration and is slightly greater than the base mud. On
the other hand, silica nanoparticles showed the lowest efficiency and an inversely proportional relationship with
the increase in concentration. Therefore, the addition of silica nanoparticles could cause problems related to the
cleaning efficiency of the drilling mud, whereas titania nanoparticles could contribute to improving it.
Figure 24: YP/PV relationship before aging
In the case of apparent viscosity (Figure 25), titania nanoparticles had the highest values, while silica nanoparticles
had the lowest. Although, this parameter does not give an exact indication of the real viscosity, it is useful to
diagnose problems when drilling. It was calculated in the present study by dividing the viscosity reading at 600
RPM by two, so that from the column chart below, it is noticed that the titania nanoparticles showed the highest
viscosities at high shear rate.
0
5
10
15
20
25
30
26 40 60 80
YP
, lb
/10
0 f
t2
TEMPERATURE, °C
YIELD POINT
BASE MUD
TiO2 0.20%
TiO2 0.60%
SiO2 0.20%
SiO2 0.60%
0.00
0.50
1.00
1.50
2.00
26 40 60 80
YP
/PV
, LB
/10
0 f
t2/c
P
TEMPERATURE, °C
YP/PV
BASE MUD
TiO2 0.20%
TiO2 0.60%
SiO2 0.20%
SiO2 0.60%
Page 30
29
Figure 25: Apparent viscosity before aging
Table 18: Summarizes the analysis for the rheological gel strength in the drilling mud samples and results of the
increase in gel strength of mud samples before aging
In the case of gel strength, the greatest increase at different temperatures was mostly in the base mud, obtaining
85.71 % at 80 °C, as it is plotted in figure 26. However, the readings at 10 seconds and 10 minutes for both
concentrations of titania nanoparticles were the largest in magnitude. Silica nanoparticles demonstrated the lowest
0.00
5.00
10.00
15.00
20.00
25.00
30.00
26 40 60 80
AV
, cP
TEMPERATURE, °C
APPARENT VISCOSITY
BASE MUD
TiO2 0.20%
TiO2 0.60%
SiO2 0.20%
SiO2 0.60%
T (°C) SAMPLE 10 sec 10 min INCREASE (%)
BASE MUD 9.5 14 47.37
TiO2 0.20% 9.5 14.5 52.63
TiO2 0.60% 12 16 33.33
SiO2 0.20% 8.5 11.5 35.29
SiO2 0.60% 9 11 22.22
BASE MUD 9 14 55.56
TiO2 0.20% 9.5 14.5 52.63
TiO2 0.60% 11 16.5 50.00
SiO2 0.20% 8 10.5 31.25
SiO2 0.60% 8 10 25.00
BASE MUD 7 12 71.43
TiO2 0.20% 8.5 14 64.71
TiO2 0.60% 10 16.5 65.00
SiO2 0.20% 6 8.5 41.67
SiO2 0.60% 7 9 28.57
BASE MUD 7 13 85.71
TiO2 0.20% 9.5 16.5 73.68
TiO2 0.60% 11.5 19.5 69.57
SiO2 0.20% 6 8 33.33
SiO2 0.60% 6 7.5 25.00
60
80
RHEOLOGY
GEL STRENGTH
BEFORE AGING
26
40
Page 31
30
values in both cases. These results indicate that addition of titania in the base mud tends to create a gel structure
quicker than the base mud over time. Moreover, this effect was more prominent when the concentration was
increased. This may however be beneficial in slowing down the settlement of drill cuttings when mud circulation
is stopped in highly deviated wells.
Figure 26: Gel strength increase over time before aging
Silica nanoparticles also showed an increase over time in gel strength parameter when the concentration was
increased, although it was minor compared to the other mud samples. In addition, these results indicate that silica
nanoparticles could reduce the performance of the drilling mud and induce operational problems, including
mechanical sticking of the drill string due to a possible accumulation of drill cuttings. However, silica nano-
particles could prove beneficial in that they could be introduced into the drilling mud to reduce the gel strength of
the drilling fluid when it is too high. Regarding gel strength classification, there was insufficient data over time
to determine if any of the mud samples showed a progressive or regressive trend. However, it is noteworthy that
there is a reduction in the percentage of the gel strength increase when the concentration of nanoparticles is raised.
This could indicate that a higher concentration of these nanoparticles produces a slow increment of the gel strength
over time. Furthermore, the increase of gel strength on the base mud and titania nanoparticles could be due to a
reduction in the water viscosity generated by an increase in temperature, which is also relevant to higher
temperature drilling operations (Gray et al. 1980).
4.3 Rheology-After Aging
In the post-aging case, the rheology was tested before stirring the mud samples in the mixer and after stirring
them. The intention of testing the mud samples before stirring them was to simulate how they could behave once
the drill string start to rotate again, after being static for a period. The evaluation after stirring them was done to
simulate their behaviour after the drilling mud have been circulated for a period. Two sets of results were therefore
obtained.
4.31 Before Stirring
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
80.0%
90.0%
26 40 60 80
INC
REA
SE, %
TEMPERATURE, °C
GEL STRENGTH INCREASE
BASE MUD
TiO2 0.20%
TiO2 0.60%
SiO2 0.20%
SiO2 0.60%
Page 32
31
Making a comparison between figures 14 and 15, there is a tangible elevation in the viscosity for both
concentrations of silica nanoparticles after the aging process before stirring the mud sample. These readings were
higher than the mud sample with titania nanoparticles and the base mud. In the case of the mud sample with titania
nanoparticles and the base mud, the viscosities decreased after the aging process. This may be attributable to
degradation of the other additives (viscosifier agent) in the base mud. The highest increase in plastic viscosity,
yield point and apparent viscosity was for silica nanoparticles; in addition, these results were also higher than the
readings at the same temperature before aging. This could indicate that after the aging process, flocculation took
place and the mechanical friction between particles increased in the drilling mud with silica nanoparticles.
Table 19: Results of PV, YP, YP/PV and AV of mud samples after aging before stirring
The results for the base mud in Table 19 indicate a decreasing trend in their rheological properties. In the case of
yield point, the values indicate that these mud samples may struggle to perform some of their functions, such as
carrying drill cuttings, after being static for a long time. A similar deduction may apply to the drilling mud with
titania nanoparticles which also exhibit a decreasing trend in yield point. Moreover, the reduction in plastic
viscosity of the base mud could be due to a reduction in the mechanical friction of the embedded nano-particles.
Table 20: Results of gel strength of mud samples after aging before stirring
In the case of gel strength, all the results showed a poor performance, as can be observed in Table 20. It is also
apparent however that the increase in gel strength in silica nanoparticles compared to the base mud, was lower
before the aging process. However, due to the low results in gel strength, it would appear that the mud samples
are not able to suspend drill cuttings after being static at borehole conditions over a long period which could cause
operational issues.
4.32 After Stirring
T (°C) SAMPLE PV (CP) YP (lb/100 ft2) YP/PV AV (cp)
BASE MUD 12.5 14 1.12 19.5
TiO2 0.20% 15 20 1.33 25
TiO2 0.60% 13.5 17 1.26 22
SiO2 0.20% 16 22 1.38 27
SiO2 0.60% 19 25.5 1.34 31.75
RHEOLOGY
PV - YP - YP/PV
AFTER AGING - BEFORE STIRRING
26
T (°C) SAMPLE 10 sec 10 min INCREASE (%)
BASE MUD 5 7 40%
TiO2 0.20% 6.5 9.5 46%
TiO2 0.60% 7 9 29%
SiO2 0.20% 6 7.5 25%
SiO2 0.60% 8 9 13%
RHEOLOGY
GEL STRENGTH
AFTER AGING - BEFORE STIRRING
26
Page 33
32
After stirring the mud samples, it can be observed at figure 15 that the viscosities readings during different shear
rates decreased further, for all the mud samples. However, a similar trend to the previous case is observed; the
highest viscosities readings were obtained with 0.60 % (w/w) SiO2, and the lowest were for the base mud without
any nano-particles.
Table 21: Results of PV, YP, YP/PV and AV of mud samples after aging after stirring
Table 22: Results of gel strength of mud samples after aging after stirring
Tables 21 and 22 shows that there were not a favourable trend on rheological properties of the drilling mud
samples after stirring them in the mixer. In fact, all the results were lower than the rheological tests before stirring.
This loss in viscosity may be directly attributable to the degradation of the viscosifier agent during the aging
process.
4.4 Lubricity
The results obtained during the lubricity test indicated that titania nanoparticles at a concentration of 0.60 % (w/w)
gave the best performance for torque compared to the other mud samples, although, a large decrease in torque
was not observed. However, taking into account that the torque readings in the base mud tended to increase over
time before and after aging, these results could be relevant. To evaluate the lubricity of the mud samples, the CoF
was calculated using equation (4). This factor provides a more accurate value for the trend of the lubricity during
the tests since it incorporates a correction factor. For the case of the base mud, the CoF for the base mud is
calculated as follows:
lbf
.poundsin.CoF
min,cMudBase 100
9405371
0
26 (10)
T (°C) SAMPLE PV (CP) YP (lb/100 ft2) YP/PV AV (cp)
BASE MUD 8.5 9.5 1.12 13.25
TiO2 0.20% 10.5 13.5 1.29 17.25
TiO2 0.60% 10 12 1.20 16
SiO2 0.20% 11 11 1.00 16.5
SiO2 0.60% 12.5 13.5 1.08 19.25
RHEOLOGY
PV - YP - AV
AFTER AGING - AFTER STIRRING
26
T (°C) SAMPLE 10 sec 10 min INCREASE (%)
BASE MUD 4 7 75%
TiO2 0.20% 4.5 7 56%
TiO2 0.60% 5 8 60%
SiO2 0.20% 4.5 6 33%
SiO2 0.60% 5 7 40%
RHEOLOGY
GEL STRENGTH
AFTER AGING - AFTER STIRRING
26
Page 34
33
3501
.CoFmin,cMudBase
026 (11)
The same calculation was performed for the rest of the mud samples. We consider again both cases before aging
and after aging.
4.41 Before Aging
From the results of the lubricity test, which can be observed from Tables 10 to 14 and from figures 16-20, it can
be appreciated that the results of titania nanoparticles at a concentration of 0.60 % (w/w) showed a decreasing
trend (and the lowest values) for the torque readings at different temperatures. However, at a lower concentration
(0.20 % w/w), they showed the highest torque readings. In the case of silica nanoparticles, at a concentration of
0.20% (w/w), the torque readings were close to the base mud and showed a stable growth over time. However,
when their concentration was raised, the torque also increased; however, these readings decreased over time,
although, they were not lower than the results of the base mud. Table 23 shows the variation in percentage of the
torque readings of the treated base mud with nanoparticles relative to the untreated base mud. Here (and also in
Table 24), a negative value means a reduction and a positive value means an increase, moreover, the results are
highlighted with a blue colour scale which gets darker with an increase in the percentage.
Table 23: Percentage in torque variation before aging
In Table 23 the highest decrease in percentage was for titania nanoparticles at 0.60 % (w/w) and the torque
percentage tended to reduce with an increase in temperature, as well as, silica nanoparticles at 0.60% (w/w).
Moreover, titania nanoparticles at 0.20 % (w/w) and silica nanoparticles at 0.20 % (w/w), both showed a
decreasing trend from 60 °C, although both of them show some fluctuation. Regarding the CoF analysis, table 24
shows the results for the torque readings at different temperatures using the same format as table 23.
SAMPLE TEMP (°C) 1 2 3 4 5 6 SPARKLINES
26 13.1% 12.7% 10.5% 11.5% 15.0% 16.4%
40 0.9% 2.1% 5.0% 9.2% 13.0% 10.2%
60 6.0% 9.2% 9.5% 8.5% 7.0% 4.4%
80 1.8% 0.5% -2.4% 1.1% -0.9% -2.1%
26 7.2% 1.3% 0.0% -1.8% -3.0% -4.3%
40 -7.3% -11.1% -11.0% -11.4% -11.8% -11.9%
60 -13.1% -13.5% -14.6% -15.7% -15.7% -16.9%
80 -10.6% -11.3% -13.6% -14.0% -15.4% -15.0%
26 -1.3% -1.8% -2.3% -0.5% 2.0% 1.5%
40 -4.0% -2.8% 0.7% 2.7% 5.2% 4.9%
60 -6.0% -3.8% -2.5% -1.6% -2.2% -3.6%
80 0.7% 0.2% -3.1% -2.4% -3.0% -5.2%
26 25.3% 17.0% 13.0% 9.5% 6.8% 9.6%
40 2.1% -1.9% -2.4% -1.9% -1.7% -1.7%
60 -2.9% 0.7% -0.9% -2.0% -3.1% -4.2%
80 2.8% 0.0% -4.0% -5.0% -6.5% -8.2%
TIME (MIN)
TORQUE VARIATION (%)
BEFORE AGING
SiO2 0.60%
SiO2 0.20%
TiO2 0.60%
TiO2 0.20%
Page 35
34
Table 24: Coefficient of friction before aging
A similar trend for the mud samples with nanoparticles is evident as in the case of table 23. Moreover, an
increasing trend in the CoF of the base mud with a rise of temperature is clearly evident in Table 24. These tables
imply that the addition of silica nanoparticles in the base mud tends to improve the lubricity, even with a small
concentration. In addition, these trends suggest that it could be necessary to increase the nano-particle
concentration to achieve better results, since the maximum reduction in torque was about 8 %. However, in the
case of titania nanoparticles the highest reduction in torque was about 16 % (double that of silica nano-particles).
The reduction in torque and CoF of titania nanoparticles at 0.60 % (w/w) would also suggest that an increase in
their concentration could further depress both parameters, with the implication that titania nanoparticles could
have a greater impact in the improvement of drilling mud lubricity than silica nanoparticles. Lubricity refers to
the reduction in friction and or wear by a lubricant and therefore the presence of titania nano-particles offers clear
tribological advantages. The tables 23 and 24 further show that the torque and CoF of the base mud increases with
temperature, whereas the addition of nanoparticles in the base mud shows the contrary effect. The reduction is
more significant with a higher concentration of titania nanoparticles and this may also be evidence for the
improved thermal conductivity (and therefore heat dissipation characteristic) of nanoparticles, which has been
emphasized in numerous experimental studies including (Choi, 1995; Hung and Gu, 2014) Due to the presence of
nanoparticles around the lubricating film created between the lubricity ring and block in the lubricity tests, the
nano-particles may have isolated and dissipated the heat more efficiently around this film. Silica and titania are
both ceramic materials which are known to have excellent thermal dissipation properties. As nano-particles these
materials retain this feature.
4.42 After Aging
In this case, the lubricity test was carried out only after stirring the mud samples and cooling them to recreate the
lubricity behaviour representative of drilling muds after circulation for some time after following a period in which
SAMPLE TEMP (°C) 1 2 3 4 5 6 SPARKLINES AVERAGE
26 0.354 0.373 0.378 0.378 0.377 0.374 0.37
40 0.399 0.400 0.396 0.391 0.384 0.388 0.39
60 0.427 0.419 0.419 0.421 0.421 0.425 0.42
80 0.412 0.419 0.430 0.432 0.435 0.440 0.43
26 0.400 0.420 0.417 0.421 0.433 0.435 0.42
40 0.403 0.409 0.416 0.427 0.434 0.428 0.42
60 0.452 0.458 0.459 0.457 0.450 0.444 0.45
80 0.419 0.421 0.419 0.437 0.431 0.430 0.43
26 0.379 0.378 0.378 0.371 0.365 0.358 0.37
40 0.370 0.356 0.353 0.346 0.339 0.342 0.35
60 0.371 0.362 0.358 0.355 0.355 0.353 0.36
80 0.368 0.372 0.371 0.372 0.368 0.374 0.37
26 0.349 0.366 0.369 0.376 0.384 0.379 0.37
40 0.383 0.389 0.399 0.401 0.404 0.407 0.40
60 0.401 0.403 0.409 0.414 0.412 0.410 0.41
80 0.414 0.420 0.416 0.422 0.422 0.417 0.42
26 0.444 0.436 0.427 0.413 0.402 0.410 0.42
40 0.408 0.393 0.387 0.383 0.378 0.381 0.39
60 0.414 0.422 0.415 0.413 0.408 0.407 0.41
80 0.423 0.419 0.413 0.411 0.407 0.404 0.41
BASE MUD
TiO2 0.20%
TiO2 0.60%
SiO2 0.20%
SiO2 0.60%
BEFORE AGING
COF
TIME
Page 36
35
they are static at the bottom hole condition. From table 15 and figure 21 (section 3) it can be observed that the
results were lower than the previous test at the same temperature (before the aging process), although, the growing
trend exhibited by the base mud remained. However, the other mud samples did not exhibit the same pattern. For
titania and silica nanoparticles at 0.60 % (w/w) the trend changed and remained stable with slight fluctuations,
while titania and silica at 0.20 % (w/w) showed a decreasing trend. Below, table 25 shows the torque variation in
percentage after the aging process compared to the base mud.
Table 25: Percentage in torque variation after aging
In this scenario, the torque variation for all the mud samples with nanoparticles showed a considerable drop after
the first minute of the test, and then, it was followed by a moderate fall over time. However, in most samples, the
reduction was not below than the torque readings of the base mud; only titania nanoparticles at 0.60 % (w/w) were
below the base mud values. Finally, Table 26 shows the results of the calculation of the CoF after aging. In general,
the results follow the same trend as the torque readings of this test. The friction factors of the mud with
nanoparticles were close to the base mud friction factor.
Table 26: Coefficient of friction after aging
In general, the results of the lubricity after the aging process demonstrated the best performance for all the mud
samples. All of these results showed a considerable reduction in the CoF compared to the results before aging.
However, only titania nanoparticles at 0.60 % (w/w) were below the friction factor of the base mud over time,
although, only a marginal decrease was achieved. Further experiments are warranted to evaluate the lubricity of
the mud samples at different temperatures both before and after aging to confirm if these nanoparticles still could
contribute to isolating heat in the lubricating film and show a decreasing trend.
5 CONCLUSIONS
An experimental study has been described to evaluate the rheological characteristics of water based muds using
nano-particles. Five mud samples were examined, namely ordinary base mud, two cases of titania nano-particle
doped water based mud and two cases of silica nano-particle doped base mud. Density, rheology (gel strength,
apparent viscosity, shear stress) and lubricity (torque and coefficient of friction) properties have been quantified
using a variety of devices. Both before aging and after aging scenarios have been studied and the influence of
TEMP (°C) SAMPLE 1 2 3 4 5 6 SPARKLINES
TiO2 0.20% 30.4% 8.8% 7.9% 3.7% 5.0% 5.3%
TiO2 0.60% 18.2% 2.1% -1.5% -2.9% -1.7% -0.6%
SiO2 0.20% 44.3% 17.9% 10.9% 6.6% 8.7% 8.2%
SiO2 0.60% 33.9% 16.7% 11.4% 10.3% 12.0% 11.4%
TORQUE VARIATION (%)
AFTER AGING
TIME (MIN)
26
TEMP (°C) SAMPLE 1 2 3 4 5 6 SPARKLINES AVERAGE
BASE MUD 0.263 0.309 0.321 0.327 0.322 0.321 0.311
TiO2 0.20% 0.343 0.337 0.346 0.339 0.338 0.337 0.340
TiO2 0.60% 0.311 0.316 0.316 0.318 0.317 0.319 0.316
SiO2 0.20% 0.380 0.365 0.355 0.349 0.351 0.347 0.358
SiO2 0.60% 0.353 0.361 0.357 0.361 0.361 0.357 0.358
TIME (MIN)
COF
AFTER AGING
26
Page 37
36
temperature in particular on rheology and lubricity characteristics examined in detail. The pertinent conclusions
from the present study may be summarized as follows:
• A small enhancement in base mud density is caused with silica nanoparticles with no tangible modification
achieved with titania nanoparticles. Before aging, titania nanoparticles achieve greater viscosity than base mud
or silica-doped mud which reduces viscosity.
• Before aging, titania nanoparticles result in higher plastic viscosity (PV), yield point (YP) and apparent viscosity
(AV) of the drilling mud, although a decreased yield point when the concentration is lower i.e. 0.20% (w/w) at
40 °C.
• Before aging, silica nanoparticles generally result in a decrease in the yield point and apparent viscosity of the
drilling mud, which may be related to super hydrophilic characteristics.
• Before aging, titania nanoparticles achieve the highest efficiency (low plastic viscosity and a high yield point)
whereas silica nanoparticles showed the lowest efficiency.
• Before aging, higher values of gel strength are associated with titania and lower values with silica nano-
particles, whereas the greatest increase in gel strength is with base mud. The introduction of titania in the base
mud generates a gel structure quicker than the base mud over time.
• After aging, and before stirring, greater plastic and apparent viscosity is achieved for silica nanoparticles and
lower viscosities with the titania nano-particles.
• After aging and before stirring, titania nanoparticles cause a reduction in the drilling mud yield point whereas
silica nano-particles cause the opposite effect.
• After aging and before stirring, the increase in gel strength in silica nanoparticles relative to the base mud is
less dramatic than before aging.
• After aging and stirring, the greatest viscosities are achieved with 0.60 % (w/w) SiO2, and the lowest are
associated with the base mud without any nano-particles.
• Before aging, with regard to lubricity, titania nanoparticles at a concentration of 0.60 % (w/w) attained the best
performance for torque (i.e. lowest torque) compared to the other mud samples, although, a significant reduction
in torque was not measured.
• Before aging, silica nanoparticles, at a concentration of 0.20% (w/w), produced torque readings close to those
of the base mud although these values increased with time i.e. worst torque performance.
• Before aging, torque and CoF of the base mud increases with temperature, whereas the addition of nanoparticles
in the base mud results in a decrease in torque and CoF with temperature indicating an increase in heat
dissipation (improved thermal conductivity) with nanoparticles.
• After aging, only titania nanoparticles at 0.60 % (w/w) achieved CoF magnitudes below the base mud values
indicating a non-trivial enhancement in lubricity.
• In general, the results of the lubricity after the aging process were superior to those before aging.
The results generally indicate that based on properties measured before the aging process, titania nanoparticles at
a concentration of 0.60% (w/w) could be used as an additive to improve the rheological properties and lubricity
of a drilling fluid, provided a stable formulation is achievable for long periods of time. In this regard they offer
some promise as robust additives for reducing the torque and drag in highly deviated and ERD wells where there
is no presence of shale. Further investigations are required however to gain deeper insight into the performance
Page 38
37
of both silica and titania (and indeed other) nano-particles in order to confirm their potential benefits for drilling
operations. The present investigation also provides some useful and much-needed rheological data for numerical
and mathematical models and efforts for calibrating such models with computational fluid dynamics codes are
presently under way. Furthermore, there is an extensive range of other metallic nano-particles which could be
explored including silver, zinc, copper etc. Also, further studies must be conducted e.g. field trials to establish if
indeed the nano-particles work in full scale operations. It is hoped that the present work will stimulate petroleum
engineers working in the field to consider this.
ACKNOWLEDGEMENTS
The authors are grateful to the reviewers for their insightful comments which have served to significantly improve
the present article.
FUNDING
This research did not receive any specific grant from funding agencies in the public, commercial, or not- for profit
sectors.
DECLARATION OF CONFLICTS OF INTEREST
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication
of this article.
REFERENCES
Abdo J, Haneef MD (2013) Clay nanoparticles modified drilling fluids for drilling of deep hydrocarbon wells.
Appl Clay Sci 86: 76–82.
Ahmet S, Mustafa VK, Reha O (2013) Performance analysis of drilling fluid liquid lubricants. J Petroleum Sci
Eng 108: 64–73.
Al-Yasiri MS, Al-Sallami WT (2015) How the drilling fluids can be made more efficient by using
nanomaterials. American J Nano-Research and Applications 3:41-45.
Amanullah Md, Al-Arfaj MK, Al-Abdullatif Z (2011) Preliminary test results of nano-based drilling fluids for
oil and gas field application. SPE Drilling Conference and Exhibition, Amsterdam, The Netherlands,
March 1-3 SPE/IADC 139534. doi:10.2118/139534-MS
Baker Hughes (1995) INTEQ., Drilling Engineering Workbook. Baker Hughes INTEQ, Houston, Texas, USA.
Bég O. Anwar, Basir MFM, Uddin MJ, Ismail AIM (2017) Numerical study of slip effects on asymmetric
bioconvective nanofluid flow in a porous microchannel with an expanding/contracting upper wall using
Buongiorno’s model. J Mechanics in Medicine and Biology 17(5): 1750059 (28 pages)
doi: 10.1142/S0219519417500592.
Behnamanhar H, Noorbakhsh SS, Maghsoudloojafari H (2014) Environmentally friendly water-based drilling
fluid for drilling of water-sensitive formations. J Petroleum and Gas Exploration Research 4(4): 60-
71.
Page 39
38
Bu H, Sun J, Wang C, Bu P (2013) Rheological properties of polymer-gel drilling fluids at high temperature
and pressure. Chemistry and Technology of Fuels and Oils 48 (6): 449–458.
Choi SUS (1995) Enhancing thermal conductivity of fluids with nanoparticles. Development of Applications of
non-Newtonian Flows. ASME J Fluids Eng. 66:99–105.
Dantas APT, Leite RS, Nascimento RCAM, Amorim LV (2014) The influence of chemical additives in filtration
control of inhibited drilling fluids. Brazilian Journal of Petroleum and Gas 8(3): 097-108.
Dingsøyr E, Pedersen E, Taugbøl K (2004) Oil Based drilling fluids with tailor-made rheological properties:
results from a multivariate analysis. Annual Transactions of the Nordic Rheology Society 12: 10-23.
FANN (2016) Retrieved from http://www.fann.com/fann/products/supplies-and-reagents/lab-equipment-
supplies/blenders-and-mixers/mixers-hb.page.
Fazelabdolabadi B, Khodadadi AA, Sedaghatzadeh M (2015) Thermal and rheological properties improvement
of drilling fluids using functionalized carbon nanotubes. Applied Nanoscience 5(6): 651–659.
Gray GR, Darley HCH, Rogers WF (1980) Composition and Properties of Oil Well Drilling Fluids. Gulf
Publishing Company, Houston, Texas, USA.
Huminic G, Huminic A (2012) Application of nanofluids in heat exchangers: A review. Renewable and
Sustainable Energy Reviews 16:5625–5638.
Hung YH, Gu HJ (2014) Multiwalled carbon nanotube nanofluids used for heat dissipation in hybrid green energy
systems. J Nanomaterials, Article ID: 196074 (12 Pages). doi:10.1155/2014/196074.
Hwang Y, Lee J, Lee J, Jeong Y, Cheong S, Ahn Y, Kim S (2008) Production and dispersion stability of
nanoparticles in nanofluids. Powder Tech.186(2):145-153.
Kaloudis E, Papanicolaou E, Belessiotis V (2016) Numerical simulations of a parabolic trough solar collector
with nanofluid using a two-phase model. Renewable Energy 97:218-229.
Kannaiyan K, Anoop K, Sadr R (2016) Effect of nanoparticles on the fuel properties and spray performance of
aviation turbine fuel. ASME J. Energy Resources Tech. 139(3):032201-032201-8.
Lin Jin, Dan Yue, Zhe-Wu Xu, Guobin Liang, Yilei Zhang, Jian-Fu Zhang, Xingcai Zhang and Zhenling Wang
(2014) Fabrication, mechanical properties, and biocompatibility of reduced graphene oxide-reinforced nanofiber
mats, RCS Adv. 4(66) 303-35041.
Mostafavi V, Ferdous MZ, Hareland G, Husein M (2011) Design and application of novel nano drilling fluids
to mitigate circulation loss problems during oil well drilling operations. Clean Tech 383-386.
OFITE (2014) OFI TESTING EQUIPMENT, INC. Retrieved from http://www.ofite.com/products/product/43-
mud-balance-4-scale-metal.
Olatunde AO, Usman MA, Olafadehan OA, Adeosun TA, Ufot OE, Improvement of rheological properties of
drilling fluid using locally based materials. Petroleum & Coal 54(1): 65-75.
Qu Y, Lai X, Zou L, Su Y (2009) Polyoxyalkyleneamine as shale inhibitor in water-based drilling fluids. Applied
Clay Science 44(3): 265-268.
Shuang Yang, Yu Hou, Bo Zhang, Xiao Hua Yang, Haimin Zhang, Hui Jun Zhao and Hua Gui Yang (2014)
Precisely controlled heterogeneous nucleation sites for TiO2 crystal growth, Cryst Eng Comm, 16, 7502-7506.
Shuang Yang, Nian Huang, Yong Mei Jin, Hui Qing Zhang, Yong Hua Su and Hua Gui Yang (2015) Crystal
shape engineering of anatase TiO2 and its biomedical applications. Cryst Eng Comm, 17, 6617-6631
Page 40
39
Slawomir R, Zbigniew KB, Malgorzata U (2009) Study on the application of starch derivatives as the regulators
of potassium drilling fluids filtration. Chemistry and Chemical Tech 3:107-202.
Ying Tian, Xingcai Zhang, Hong-Zhang Geng, Hai-Jie Yang, Chungang Li, Shi-Xun Da, Xiushan Lu, Jie Wang
and Song-Lin Jia (2017) Carbon nanotube/polyurethane films with high transparency, low sheet resistance
and strong adhesion for antistatic application, RSC Adv., 7(83), 53018-53024.
Yuri M. Lvov, Pravin Pattekari, Xingcai Zhang, Vladimir Torchilin, Converting poorly soluble materials into
stable aqueous nanocolloids, Langmuir 27 (3), 1212-1217 (2011).
Zakaria M, Husein MM, Harland G (2012) Novel nanoparticle-based drilling fluid with improved characteristics,
SPE International Oilfield Nanotechnology Conference and Exhibition, 12-14 June, Noordwijk, The
Netherlands.
APPENDIX
Properties of nano-particles used in the experiments
Table A1 Properties of Titanium Oxide 2OTi Nanoparticles (US Research Nanomaterials, Inc, 2016).
Titanium Oxide (Ti 02) Nanoparticles
Properties
Purity 99.9%
Average Particle Size 30 nm
Specific Surface Area 35 – 60 𝑚2 𝑔⁄ r
Colour White
Morphology Near Spherical
Bulk Density 0.25 𝑔𝑟 𝑐𝑚3⁄
True Density 4.23 𝑔𝑟 𝑐𝑚3⁄
Table A2: Properties of Silicon Dioxide 2OSi Nanoparticles (US Research Nanomaterials, Inc, 2016)
Silicon Dioxide (Si02) Nanoparticles
Properties
Purity 96.3%
Average Particle Size 20 – 30 nm
Specific Surface Area 130 – 600 𝑚2 𝑔⁄ r
Colour White
Bulk Density <0.10 𝑔𝑟 𝑐𝑚3⁄
True Density 2.4 𝑔𝑟 𝑐𝑚3⁄
.
